Patent document 1 discloses a pharmaceutical composition comprising a therapeutically effective amount of a drug, a solubilizer and a release modulator, wherein the release of the drug and the solubilizer is synchronized. However, the document does not describe a matrix tablet-type sustained-release preparation relating to pioglitazone.
Patent document 2 discloses a preparation comprising a core component comprising at least one water-soluble active ingredient, a lipid system comprising at least one lipid, at least one water-insoluble release modifier, at least one channel forming factor, in some cases, one or more pharmaceutical additives and one or more coating factors. However, the document does not describe a matrix tablet-type sustained-release preparation relating to pioglitazone.
Patent document 3 discloses a hydrogel-type sustained-release preparation comprising (1) at least one drug, (2) an additive for penetration of water into the core of the preparation and (3) a hydrogel-forming polymer, wherein said preparation is capable of undergoing substantially complete gelation during its stay in the upper digestive tract including stomach and small intestine and is capable of releasing the drug in the lower digestive tract including colon. However, the document does not describe a matrix tablet-type sustained-release preparation relating to pioglitazone.
The preparation of patent document 3 achieves a stable sustained-release effect, since the drug is dissolved and absorbed fine also in the colon. Since pioglitazone shows low absorbability in the colon, it is not suitable for direct application.